Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
  • H01J37/08—Ion sources; Ion guns
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/26—Bombardment with radiation
  • H01L21/263—Bombardment with radiation with high-energy radiation
  • H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/48—Ion implantation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
  • H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation

Definitions

• the invention relates generally to ion implantation and, more particularly, to ion sources that use a boron-based source feed gas and methods associated with the same.
• Ion implantation is a conventional technique for introducing dopants into materials such as semiconductor wafers. Dopants may be implanted in a material to form regions of desired conductivity. Such implanted regions can form active regions in resulting devices (e.g.. semiconductor devices).
• a source feed gas is ionized in an ion source. The ions are emitted from the source and may be accelerated to a selected energy to form an ion beam. The beam is directed at a surface of the material and the impinging ions penetrate into the bulk of the material and function as dopants that increase the conductivity of the material.
• Conventional ion sources may have limitations under certain implantation conditions. For example, conventional ion sources may operate inefficiently at low extraction energies and/or low beam currents which may be used in implantation processes that form implanted regions having ultra-shallow junction depths. As a result, long implant times may be needed to achieve a desired implantation dose and, thus, throughput is adversely affected.
• a method of implanting ions comprises generating C 2 BjOH x ions from C 2 B JO H J2 and implanting the C 2 BioH x ions in a material.
• an ion source is provided.
• the ion source comprises a chamber housing defining a chamber and a source feed gas supply configured to introduce C2B K )H 12 into the chamber, wherein the ion source is configured to ionize the source feed gas within the chamber into C 2 BioH x ions.
• FIG. 1 illustrates an ion implantation system according to an embodiment of the invention.
• FIG. 2 illustrates an ion source according to an embodiment in the invention.
• FIG. 3 is a plot of optimal mass spectrum for carborane for use in ion implantation.
• the methods involve generating ions from a source feed gas that comprises multiple elements.
• the source feed gas may comprise boron and at least two other elements.
• the use of such source feed gases can lead to a number of advantages over certain conventional processes including enabling use of higher implant energies and beam currents when forming implanted regions having ultra-shallow junction depths.
• the composition of the source feed gas maybe selected to be tihermally stable at relatively high temperatures (e.g., greater than 350 0 C) which allows use of such gases in many conventional ion sources (e.g., indirectly heated cathode, Bemas) which generate such temperatures.
• FIG. 1 illustrates an ion implantation system 10 according to an embodiment of the invention.
• the system includes an ion beam source 12 that generates an ion beam 14 which is transported through the system and impinges upon a wafer 16.
• the ion beam source includes a source feed gas supply 17.
• the source feed gas supply may generate the source feed gas from a source feed material, as described further below.
• Source feed gas from the supply is introduced into the ion beam source and is ionized to generate ionic species.
• the source feed gas may comprise boron and at least two other elements (e.g.. X ⁇ B b Y c ) according to certain embodiments of the invention.
• an extraction electrode 18 is associated with the ion beam source for extracting the ion beam from the source.
• a suppression electrode 20 may also be associated with the ion source.
• the implantation system further includes a source filter 23 which removes undesired species from the beam. Downstream of the source filter, the system includes an accelerationydeceleralion column 24 in which the ions in the beam are accelerated/decelerated to a desired energy, and a mass analyzer 26 which can remove energy and mass contaminants from the ion beam through use of a dipole analyzing magnet 28 and a resolving aperture 30.
• a scanner 32 may be positioned downstream of the mass analyzer and is designed to scan the ion beam across the wafer.
• the system includes an angle corrector magnet 34 to deflect ions to produce a scanned beam having parallel ion trajectories.
• the scanned beam impinges upon the surface of the wafer which is supported on a platen 36 within a process chamber 38.
• the entire path traversed by the ion beam is under vacuum during implantation.
• the implantation process is continued until regions having the desired dopant concentration and junction depth are formed with the wafer.
• Suitable systems include implaniers having a ribbon beam architecture, a scanned-beam architecture or a spot beam architecture (e.g., systems in which the ion beam is static and the wafer is scanned across the static beam).
• implaniers having a ribbon beam architecture, a scanned-beam architecture or a spot beam architecture (e.g., systems in which the ion beam is static and the wafer is scanned across the static beam).
• suitable implanters have been described LQ U.S. Patent Nos.4,922,106, 5,350,926 and 6,313,475.
• ion sources of the invention may be preferred to use in methods that form ultra-shallow junction depths (e.g., less than 25 nanometers ' ), it should be understood that the invention is not limited in this regard. It should also be understood that the systems and methods may be used to implant ions in a variety of materials including, but not limited to, semiconductor materials (e.g., silicon, silicon-on- insulator, silicon germanium. Hl-V compounds, silicon carbide), as well as other material such as insulators (e.g.. silicon dioxide) and polymer materials, amongst others.
• semiconductor materials e.g., silicon, silicon-on- insulator, silicon germanium. Hl-V compounds, silicon carbide
• insulators e.g. silicon dioxide
• polymer materials amongst others.
• source feed gas supply 17 introduces a source feed gas into the ion beam source.
• the source feed gas may comprise boron and at least two additional elements (i.e., elements that are different than boron and each other).
• the additional (i.e., non-boron) elements of the source gas may be any suitable element including carbon, hydrogen, nitrogen, phosphorous, arsenic, antimony, silicon, tin, and germanium, amongst others.
• the source feed gas may have any suitable chemical structure and the invention is not limited in this regard.
• the source feed gas XBY may be represented by other equivalent chemical formulas that, for example, may include the same elements in a different order such as BXY (e.g., BjNjH ⁇ ) or XYB.
• the source feed gas may be represented by the X 1 BbYc, wherein a > 0, b > 0 and c >0. It should be understood that in each chemical formula herein, a, b and c are greater than zero.
• Y in the above-noted formulas represents at least hydrogen (e.g., the source feed gas comprises X a B b H c ).
• derivatives of X a B b H c may be used which contain other elements or groups of elements (e.g., CHj) which replace hydrogen at X and/or B sites.
• the subsu ' tuents may be any suitable inorganic or organic species.
• X in the above-noted formulas represents at least carbon (e.g., the source feed gas comprises C a B b H c ). It should be understood that, in some embodiments, derivatives of C 3 B b Hc may be used which contain other elements or groups of elements which replace hydrogen at C and/or B sites). The substituents may be any suitable inorganic or organic species. In some cases, it may be preferred that the source feed gas comprise C.B 10 H 12 .
• X in the above-noted formulas may be one or more of N, P 1 As, Sb, Si, Ge or Sn.
• the source feed gas may comprise N a B b Yc (e.g., N a BioHi2 or B 3 N 3 H 6 ), N 8 B b H 0 . P 11 B b H 0 , As a B b H c . Sb 3 BhHc, Si 0 B 11 Hc, Ge3 b H c and Sn 2 BtHc.
• other elements or groups of elements may replace hydrogen at the X and/or B sites.
• X and Y are typically selected so as not to introduce species that impart overly undesirable properties to the material which, for example, impair device performance.
• species may include sodium, iron and gold, amongst others.
• the source feed gas may be ionized to form a variety of different ion species.
• the ion species may include the same, or similar, boron content as the source feed gas.
• the ion species may also include the additional elements present in the source feed gas.
• a source feed gas comprising X a B b Y c (e.g., X 3 B b H c ) may be ionized to form ion species comprising X n B h Y 0 '1 (e.g., X a B b H c " ') or X 3 B b Yc + ' (e.g., X 0 BbH 0 +1 ).
• the source feed gas comprises C ⁇ BioHu
• some ionic species produced include, for example,
• C ⁇ BjoH ⁇ C2B1 0 H12
• C2B1 0 H12 C2B1 0 H12
• Some other ionic species of C ⁇ BtoHu may include species derived from C 2 B1 0 H 12 , such as, for example. (C ⁇ BioHs)*. It should also be understood that the ion species may include boron and only one of the elements (e.g., Y). In some embodiments, systems of the invention include mechanisms for selecting desired ionic species from those produced for the ion beam and subsequent implantation.
• the source feed gas has a relatively high molecular weight ⁇ wKiclTcWle!iyio ⁇ fo ⁇ nati ⁇ Tro ⁇ oTis ' & molecular weighT(s)rF ⁇ r ⁇ example, it may be possible to produce ions having the desired molecular weight by appropriately selecting the ionization conditions.
• the implant depth of an ion depends on the implantation energy and its molecular weight. Increasing the molecular weight of an ion allows use of higher implant energies to achieve the same implant depth.
• source feed gases having a relatively high molecular weight can enable formation of ultra-shallow junction depths (e.g., less than 25 nm) at implant energies sufficiently high to allow operation at desirable efficiency levels.
• a relatively high implant energy e.g., 14.5 keV
• the equivalent boron implant energy is about 1 keV (for the case when all of the boron atoms are present as 11 B so that (C 2 BioH ⁇ ) + has a weight of 145 amu).
• Molecular weight of the source feed gas (and the ionic species which are implanted) is determined by the number and type of atoms in the composition. In some cases, it is preferable for b in the above-noted formulas to be greater than 2: or, more preferably, greater than 8. In some cases, it is preferable for c in the above-noted formulas to be greater than 2; or, more preferably, greater than 8. In some embodiments, it is preferred for the molecular weight of the source feed gas (and the ionic species which are implanted) to be greater than 50 amu; or, in some cases, greater than 100 amu (e.g.. about 120 amu).
• the above-noted source feed gas compositions may be present in different isomeric forms. That is. the gases may have the same chemical formula, while having a different chemicaJ structure
• the source feed gas comprising C2B 10 H 12 may be present as ortho-, meta-, or para-carborane forms. It should also be understood that the source feed gas may be present in different derivative forms.
• boron (or any other element) may be present in the source feed gas in any suitable isotope form including the naturally occurring form (e.g., 11 B - 80%, 10 B - 20%) .
• boron may be present with an atomic weight of 11 (i.e., 11 B) or an atomic weight of 10 (i.e., 10 B).
• substantially all of the boron in the source feed gas may be a single isotope 10 B or 11 B. The invention is not limited in this regard.
• lhe source feed gas has a relatively high decomposition temperature.
• the decomposition temperature is determined, in part, by the stability of the chemical structure.
• the composition and structure of the source feed gas may be selected to provide thermal stability at relatively high temperatures (e.g.. greater than 350 0 C) which allows use of such gases in many conventional ion sources (e.g.. indirectly heated cathode, Bernas) which generate such temperatures.
• the decomposition temperature of the source feed gas may be greater than 350 0 C; in some cases, greater than 500 °C; and, in some cases, greater than 750 0 C.
• source feed gases that comprise boron and at least two additional elements may be suitable for use in conventional ion sources in which relatively high temperature (e.g., greater than 350 0 C) are used.
• relatively high temperature e.g., greater than 350 0 C
• the decomposition temperature depends on the specific source feed gas used and the invention is not limited in this regard.
• the source feed gas supply supplied to the ion source is generated directly from a source feed material.
• the source feed gas may be generated in any suitable manner.
• the source feed material may be a solid and, for example, be in a powder form.
• the .source feed materia] is a liquid.
• the source feed gas can be produced via a sublimation and/or evaporation step of a material that comprises boron and at least two additional elements. It should also be understood that the source feed gas may be conventionally available in gaseous form and can be directly supplied to the ion source without the need for the separate generation step. The manner in which the source feed gas is generated and/or supplied depends, in part, on the composition of the source feed gas. JLn some embodiments, the source feed material comprises boron and at least two additional elements including any of the compositions noted above. In some of these embodiments, the source feed gas generated from the source feed material also comprises boron and at least two additional elements (e.g., XBY wherein Y is not hydrogen).
• the ion species generated may also include boron and only the single element (e.g., Y), where Y is not hydrogen.
• the source feed gas comprising boron and at least two additional elements is a single gaseous compound.
• the source feed gas is provided as a single gaseous composition .
• the source feed gas may be a mixture of more than one type of gas which provides the source feed gas composition of boron and at least two additional elements. The more than one type of gas may be mixed prior to entering the ion source or inside of the ion source chamber.
• FlG. 2 illustrates ion beam source 12 according to one embodiment of the invention.
• the source includes a chamber housing 50 which defines a chamber 52 and an extraction aperture 53 through which ions are extracted.
• a cathode 54 is positioned within the chamber.
• a filament 56 is positioned outside the arc chamber in close proximity to the cathode.
• a filament power supply 62 has output terminals connected to the filament. The filament power supply heats the filament which in turn generates electrons which are emitted from the filament..
• ion beam sources having this general configuration are known as "indirectly heated cathode" (IHC) ion sources.
• An arc power supply 58 has a positive terminal connected to the chamber housing and a negative terminal connected to the cathode. The power supply accelerates electrons emitted by the cathode into the plasma generated in the chamber.
• a reflector 64 is positioned within the chamber at an end opposite the cathode.
• the reflector can reflect electrons emitted by the cathode, for example, in a direction towards the plasma within the chamber.
• the reflector may be connected to a voltage supply which provides die reflector with a negative charge; or, the reflector may not be connected to a voltage supply and may be negatively charged by absorption of electrons.
• a source magnet (not shown) produces a magnetic field within the chamber.
• the source magnet includes poles at opposite ends of the chamber. The magnetic field results in increased interaction between the electrons emitted by the cathode and the plasma in the chamber.
• Source feed gas from supply 17 is introduced into the chamber.
• the plasma within the chamber ionizes the source feed gas to form ionic species
• a variety of ionic species may be produced which depend upon the composition of the source feed gas, as noted above, and desired ionic species may be selected for the ion beam and subsequent implantation.
• ion source configurations may be used in connection with the methods of the invention.
• Bernas ion sources may be used.
• ion sources that generate plasma using microwave or RF energy may be used.
• one advantage of certain embodiments is the ability to use the source feed gas in ion sources that generate relatively high temperatures (e.g.. greater than. 350 0 C) without the source feed gas decomposing.
• "cold wall" ion sources may be used that ionize the source feed gas by using one or more electron beams. Such ion sources have been described in U.S. Patent No. 6,686,595 which is incorporated herein by reference.
• FIG. 2 may include a variety of modifications as known to those of ordinary skill in the art.
• FlG. 3 is a plot of optimal mass spectrum for carborane for use in ion implantation.
• FIG. 3 is normalized and compares beam current to molecular weight of the extracted carborane ions for an optimized carborane source feed gas and a non-optimized carborane source feed gas.
• the optimal molecular weight of carborane for implant into a wafer is preferably between 132 and 144 amu, and more preferably between J 36-138 amu.
• An optimized carborane souice feed gas may not disassociate during the ionization process as much as a non-optimized carborane source feed gas.
• an optimal carborane source feed gas results in greater beam current than a non-optimized carborane source feed gas (illustrated as “Broken-Up Beam Spectrum”)-
• This non-optimized carborane source feed gas includes at least some break-up during ionization.
• the optimal carborane source feed gas was found in one experiment to result in as much as twice the measured beam current compared to the non-optimal carborane source feed gas. Due to break-up during the ionization process, measured beam currents at molecular weights below 132 amu were substantially higher for a non-optimized carborane source feed gas than an optimized carborane source feed gas.

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• 2006
  • 2006-08-15 US US11/504,355 patent/US20070178679A1/en not_active Abandoned
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